Variations in Micromachined Isolator Geometries for Sensor Performance in Harsh Environments

This article details the design, simulation, fabrication, and testing of four variations of micromachined vibration isolators. The vibration isolators serve as low-pass filters to attenuate high-frequency (>2 kHz) mechanical excitation in order to improve both microelectromechanical system (MEMS) sensor fidelity and lifespan. Isolators are designed for integration with a small (~3 mm x ~3 mm) MEMS sensor package and boast a sub-1-cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> footprint (7 mm x 7 mm). For all isolator variations, the fundamental geometry consists of an outer frame to be fixed to the substrate of interest, a central platform to accommodate the isolated sensor, and springs for the attachment of the frame and platform. We fabricate devices via a simple, double-sided lithography process using (100) silicon-on-insulator (SOI) wafers. We then performed laser Doppler vibrometry to investigate the frequency response of each isolator variation across a 6.2-kHz bandwidth. Dependent upon geometry, isolator variations exhibit resonant frequencies from 1.3 to 2 kHz with quality factors (Q's) ranging from 16.7 to 60.